BackgroundFrailty is now seen as a significant factor in older people with diabetes, whose mortality and disability increased. This study aims to investigate the association between calf circumference (CC) with frailty in diabetic adults aged over 80 years.MethodsA cross-sectional analysis was performed on the data of 426 diabetic adults aged over 80 years. On admission, demographic data and laboratory parameters were recorded. CC was measured on the lower right leg at the point of the maximal circumference. All participants accepted frailty assessments. Frailty was mainly defined using the Fried frailty phenotype criteria.ResultsThe CC levels were significantly lower in the frail than the non-frail (26.7 ± 4.0 vs. 31.2 ± 4.0, P < 0.001). CC was negatively correlated with the Fried frailty phenotype index (P < 0.001). Logistic regression analysis of frailty revealed that age (Odds Ratio (OR), 1.368; 95% Confidential Interval (CI) 1.002–1.869; P = 0.049), CC (OR, 0.756; 95%CI 0.598–0.956; P = 0.019) were independent impact factors of frailty after adjusting all the potential confounders. Participants with low CC tertile had a significantly higher Fried frailty phenotype index than those with high CC tertiles. The best CC cut-off value for predicting frailty was 29.3 cm, its sensitivity was 75.0%, and the specificity was 78.6%, and areas under the curve (AUC) was 0.786 (P < 0.001).ConclusionsCC was strongly related to frailty in diabetic adults aged over 80 years, suggesting that CC may be helpful for monitoring physical frailty in older adults in clinical and research settings.